1. Field of the Invention
The present invention relates to a method of producing a metal-containing single-phase composition. The invention relates primarily to the production of titanium silicon carbide and composite compounds belonging to the same family.
2. Description of the Related Art
Oxygen-free combustion synthesis, also known as SHS (Self-propagating High Temperature Synthesis) is used generally in the production of intermetallic products and ceramic compositions.
In SHS technology, a mixture of two or more materials is ignited locally through the medium of an intensive heat source. This source may, for instance, consist of a heating coil or some other heating element, a laser beam, or an electron beam. The local ignition results in a local reaction, as a result of a powerful exothermic reaction. This causes the release of surplus energy, which ignites adjacent parts of the material and finally the whole of the material. This chain reaction is very rapid and, when the reaction is controlled, provides a highly effective way of mass-producing intermetals and ceramics. The highest temperature that can be reached by the system is the adiabatic temperature.
Many attempts to produce Ti3SiC2 have been made since the middle of the 1980's. Pampuch et al. (R. Pampuch et al., “Solid Combustion Synthesis of Ti3SiC2, J. EUR. CERAM. SOC., 5, 283-87 (1989)) and others have ignited a powder mixture of Ti, Si, and C in an inert atmosphere. This resulted in Ti3SiC2 + about 10-30% of other phases, such as TiC, TiSi2 and SiC.
Goesmann et al. (F. Goesmann et al., “Preparation of Ti3SiC2 by ElectronBeam-Ignited Solid-State Reaction”, J. Amer. Ceram. Soc., 81, 11, 3025-28 (1998)) believed that SHS would not result in a predominantly single phase consisting of Ti3SiC2 due to outgassing of metallic silicon as a result of the extremely high temperature of the reaction, above 2000° C. Goesmann commenced with a mixture of Ti and SiC with a chemical composition of Ti3SiC2+12.5 weight-% surplus silicon. He used an electron beam to ignite the mixture. The mixture was treated in three stages, namely heat treatment at 800° C., ignition at 900° C., followed by heat treatment at 1600° C. to achieve outgassing of surplus silicon. This method resulted in less than 8% of secondary phases in the sample.
In our own U.S. Patent Application No. 09/469,893 from December 1999, we have shown that atmospheric oxygen influences the thermal stability of Ti3SiC2 in the production process and also in the subsequent sintering process, by forming gaseous SiO, which is fundamentally different to vaporization of silicon due to high temperatures.
Thus, it has been found difficult to produce titanium silicon carbide in the aforesaid manner without obtaining other reaction products.
It has been mentioned above that the invention also relates to compositions in the same family. The family can be designated as being a single phase composition M3SiZ2, where M is at least one metal, and Z is at least one of the chemical elements C (carbon) and N (nitrogen).
The present invention relates to the problem of high costs in respect of the production of titanium silicon carbide.